Geogebra/C3/Relationship-between-Geometric-Figures/English-timed
From Script | Spoken-Tutorial
Title of script: Relationship between different Geometric Figures
Author: Madhuri Ganapathi
Keywords: video tutorial
| Visual Cue | Narration |
|---|---|
| 00:00 | Hello. |
| 00:01 | And welcome to the spoken tutorial on Relationship between different Geometric Figures in Geogebra |
| 00:07 | We assume that you have the basic working knowledge of Geogebra. |
| 00:11 | If not, please go through the “Introduction to Geogebra” tutorial before proceeding further. |
| 00:18 | Please note that the intention to teach this tutorial is not to replace the actual compass box. |
| 00:24 | Construction in GeoGebra is done with the view to understand the properties. |
| 00:29 | In this tutorial we will learn to construct
|
| 00:32 | Cyclic quadrilateral and In-circle |
| 00:35 | To record this tutorial I am using
Linux operating system |
| 00:39 | Ubuntu Version 10.04 LTS |
| 00:43 | And Geogebra Version 3.2.40.0 |
| 00:48 | We will use the following Geogebra tools for the construction
|
| 01:02 | Let us switch on to the Geogebra window. |
| 01:05 | To do this let us click on applications, Education and Geogebra.
|
| 01:13 | Let me resize this window. |
| 01:18 | Click on the options menu click on font size and then on 18 point to make the figure clear.
|
| 01:25 | Let us construct a cyclic quadrilateral. |
| 01:27 | To do this let us select the "Regular Polygon" tool from the tool bar click on the "Regular Polygon" tool click on any two points on the drawing pad. |
| 01:38 | We see that a dialog box open with a default value '4'. |
| 01:42 | click OK.
|
| 01:43 | A square 'ABCD' is drawn.
|
| 01:46 | Let's tilt the square Using the “Move” tool which is at the left corner. |
| 01:51 | Select the "Move" tool from the tool bar, click on the Move tool |
| 01:56 | Place, the mouse pointer on 'A' or on 'B'. I will choose B |
| 02:01 | Place the mouse pointer on B and drag it with the mouse. We see that the square is in the tilted position now. |
| 02:10 | Let's construct a perpendicular bisector to the segment 'AB'. |
| 02:15 | To do this Let's Select “Perpendicular bisector” tool from the tool bar. |
| 02:20 | Click on the "Perpendicular bisector" tool. |
| 02:22 | click on the point 'A' |
| 02:24 | and then on point'B' |
| 02:26 | We see that a "Perpendicular bisector" is drawn. |
| 02:30 | Let's construct a second perpendicular bisector to segment 'BC' to do this |
| 02:36 | Select “perpendicular bisector” tool from the tool bar, click on the “perpendicular bisector” tool. |
| 02:42 | click on the point 'B' |
| 02:44 | and then on point 'C' |
| 02:46 | We see that the perpendicular bisectors intersect at a point . |
| 02:50 | Let us mark this point as 'E' |
| 02:54 | Let's now construct a circle with centre as 'E' and which passes through C . |
| 03:01 | Let's select the "circle with centre through point" tool from tool bar click on the "circle with centre through point" tool. |
| 03:09 | Click on point 'E' as centre and which passes through 'C'. Click on the point 'E' and then on point 'C'. |
| 03:18 | We see that the circle will passes through all the vertices of the quadrilateral.A Cyclic Quadrilateral is drawn. |
| 03:29 | Do you know , that the cyclic quadrilateral has maximum area among all the quadrilaterals of the same sequence of side lengths. |
| 03:37 | Let's use the "Move" tool, to animate the figure. |
| 03:42 | To do this Let's select the "Move" tool from the tool bar, click on the "Move" tool place the mouse pointer on 'A' or 'B'. I will choose 'A'. |
| 03:52 | Place the mouse pointer on 'A' and drag it with the mouse to animate. |
| 03:58 | To verify that the construction is correct. |
| 04:01 | Let's now save the file. |
| 04:04 | Click on "File" "Save As". |
| 04:07 | I will type the file name as "cyclic_quadrilateral" |
| 04:21 | and click on save |
| 04:23 | Let us now open a new geogebra window to construct an incircle. |
| 04:28 | To do this Let's select on File and New. |
| 04:35 | Let's now construct a triangle to do this , Let's select the "Polygon" tool from the tool bar, Click on the "Polygon" tool. |
| 04:44 | click on the points A,B,C and A once again to complete the triangle figure. |
| 04:52 | Let's measure the angles for this triangle, |
| 04:55 | To do this Let's select the "Angle" tool from the tool bar, click on the Angle tool.
|
| 05:00 | Click on the points 'B,A,C' , 'C,B,A' and 'A,C,B'. |
| 05:15 | We see that the angles are measured. |
| 05:18 | Lets now construct angle bisectors to these angles. |
| 05:21 | Select the "Angle bisector" tool from the tool bar, |
| 05:25 | click on the "Angle bisector" tool.Click on the points 'B,A,C' . |
| 05:32 | Let's select the "Angle bisector" tool again from the tool bar to construct second angle bisector. |
| 05:39 | click on the "Angle bisector" tool and the tool bar, click on the points A,B,C. |
| 05:48 | We see that the two angle bisectors intersect at point . |
| 05:52 | Let's mark this point as 'D'. |
| 05:55 | Let's now construct a perpendicular line which passes through point D and segment AB. |
| 06:02 | Select “perpendicular line” tool from tool bar,click on the “perpendicular line” tool, click on the point D and then on segment AB. |
| 06:12 | We see that the perpendicular line intersects segment AB at a point. |
| 06:17 | Let's mark this point as 'E'. |
| 06:20 | Let's now construct a circle with centre as D and which passes through 'E'. |
| 06:27 | Let's select the "compass" tool from tool bar , click on the "compass" tool,click on the point D as centre and DE as radius. |
| 06:37 | Click on the point 'D' and then on point 'E' and 'D' once again to complete the figure. |
| 06:46 | We see that the circle touches all the sides of the triangle. |
| 06:50 | An in-circle is drawn. |
| 06:53 | With this we come to an end of this tutorial.
|
| 06:57 | To Summarize |
| 07:02 | In this tutorial we have learnt to construct |
| 07:05 | cyclic quadrilateral and |
| 07:07 | In-circle using the Geogebra tools. |
| 07:10 | As an assignment i would like you to draw a triangle ABC |
| 07:15 | Mark a point D on BC, join AD |
| 07:19 | Draw in-circles form triangles ABC, ABD and CBD of radii r, r1 and r2 . |
| 07:28 | BE is the height h |
| 07:30 | Move the vertices of the Triangle ABC |
| 07:33 | To verify the relation. |
| 07:35 | (1 -2r1/h)*(1 - 2r2/h) = (1 -2r/h) |
| 07:43 | The output of the assignment should look like this. |
| 07:52 | Watch the video available at this URL. |
| 07:55 | It summarises the Spoken Tutorial project. |
| 07:57 | If you do not have good bandwidth, you can download
and watch it |
| 08:02 | The Spoken Tutorial Project Team :Conducts workshops using spoken tutorials. |
| 08:06 | Gives certificates to those who pass an online test |
| 08:09 | For more details, contact us contact@spoken-tutorial.org |
| 08:16 | Spoken Tutorial Project is a part of Talk to a Teacher project |
| 08:19 | It is supported by the National Mission on Education through ICT, MHRD, Government of India. |
| 08:25 | More information on this Mission is available at this link. |
| 08:29 | This is Madhuri Ganapathi from IIT Bombay signing off
Thanks for joining. |
Contributors and Content Editors
Madhurig, Minal, Nancyvarkey, PoojaMoolya, Pratik kamble, Sandhya.np14
